1. Field of the Invention
This invention relates to telecommunications apparatus and methods. More particularly, this invention relates to apparatus and methods for transmitting signal (specifically signals with information or a data content) in multiple different formats.
The formats may simply be alternative technical representations of the same information; for example, different graphics formats. Alternatively, each format may be in a different medium; for example, image, text and audio formats. Further, the formats may represent something of the same information content but using different volumes of data; for example, a text file and a facsimile image made up of the characters of the text represent different formats for the same text information.
2. Related Art
In conventional telecommunications, a given user is associated with a given telecommunications terminal (e.g. a conventional telephone, or a computer with a modem, or a facsimile unit). However, more recently, users have become mobile. In addition to mobile telephones (for example digital cellular telephones such as those conforming to the GSM standard) other types of portable terminals include pagers (either tone pagers or message pagers which can receive short textual messages and display them); so called "personal digital assistants" (PDA's) and portable facsimile or computer units adapted to communicate via cellular networks using dedicated modems.
At the same time, the volume of different types of formats within which information can be transmitted is increasing, and new, so called "multi-media" formats, consisting of single sets of information presented in multiple media (such as for example image, text and audio files) are entering use.
The telecommunications channels through which information is delivered comprise channels of varying bandwidth, including optical fibre links; coaxial copper links; conventional subscriber telephone lines; infra-red local area networks; and radio transmission channels. Of these, radio frequency channels are used for mobile communications. However, radio frequency channels generally have available the lowest bandwidth due to demands on the RF spectrum and to the channel conditions within the RF spectrum.
It is becoming increasingly common for large organisations to provide local area networks within a building or group of buildings, at which a number of different terminals of different types are provided. For example, powerful workstations such as Sun (TM) workstations, may be connected on the same network as less powerful personal computers, advanced telephones, and conventional telephones. Depending on the access conditions, different users may have access to a number of different terminals within such a network, each with different capabilities of receiving information in different formats.
Various prior proposals have been made to attempt to meet the needs of mobile users dealing with data in different formats. For example, our earlier application WO 95/30317 (agents ref: A24847 WO) describes an "agent based" telecommunications system in which the position of a mobile user is tracked and, when he is in a cell which permits only low bandwidth information transfer, the incoming signal is either cached for later retrieval or the link is down graded (e.g. from video to voice).
Similarly, the article "The network with smarts, new agent--based WANs presage the future of connected computing", Andy Reinhardt, BYTE October 1994, pages 51-64, describes the proposed IBM `Intelligent Communications` service (apparently intended to be marketed in late 1995) which allows a user to set up a routing profile so that when a fax is received for the user it may be converted to text using optical character recognition, and then converted to speech and read into a voice mailbox.
Our earlier application WO 95/15635 (agents ref: A24682 WO), describes an agent based telecommunications system for use in a multiple services network.
Our earlier application WO 96/25012, filed 7 Feb. 1996 (agents ref: A24966) describes a multimedia telecommunications system employing reconfigurable agents. Aspects of this document are incorporated by reference herein.